JP6685802B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine equipped with a valve mechanism having a DOHC structure.

  In an internal combustion engine equipped with a valve mechanism with a DOHC structure in which an intake-side camshaft and an exhaust-side camshaft are provided on a cylinder head, it is necessary to transmit the power of the crankshaft to the intake-side camshaft and the exhaust-side camshaft on the way. There is an example in which an idle chain sprocket and an idle gear are interposed (for example, refer to Patent Document 1).

JP, 2005-178817, A

  In the internal combustion engine disclosed in Patent Document 1, an intake-side camshaft and an exhaust-side camshaft are rotatably supported by being sandwiched between two bearing walls of a cylinder head and a camshaft holder, respectively, and an intake-side camshaft is provided. An intake side driven gear and an exhaust side driven gear are respectively fitted to respective end portions of the exhaust side and the exhaust side camshaft that protrude from the bearing wall, and an idle gear that meshes with both the intake side driven gear and the exhaust side driven gear. Is provided coaxially with the idle chain sprocket, and the cam chain is bridged between the idle chain sprocket and the drive chain sprocket fitted to the crankshaft, and the power of the crankshaft is transmitted to the idle chain sprocket via the cam chain. The rotation of the idle gear is transmitted to the idle gear, and the rotation of the idle gear is the driven gear on the intake side and the driven gear on the exhaust side. It is transmitted to the exhaust camshaft and an intake camshaft through the mesh, to rotate the exhaust camshaft and the intake camshaft in synchronism with the rotation of the crankshaft.

  The coaxial coaxial idle gear and idle chain sprocket are rotatably supported on a support shaft that is installed between the outer wall of the cylinder head and the bearing wall. The gear is arranged on the outer wall side away from the bearing wall (see FIG. 8 of Patent Document 1).

The camshaft (intake-side camshaft, exhaust-side camshaft) is supported by the upper-end bearing part that extends upward without being displaced in the axial direction of the bearing wall, so it meshes with an idle gear that is far from the bearing wall. Therefore, the driven gears (intake-side driven gears and exhaust-side driven gears) are fitted to the ends of the camshafts that project from the bearing wall in the axial direction across the idle chain sprockets (see FIG. 8 of Patent Document 1). .
Therefore, the intake-side driven gear and the exhaust-side driven gear, which have large diameters, are arranged at the ends of the intake-side camshaft and the exhaust-side camshaft, which have long axial lengths and project away from the bearing wall. Axial width increases and size increases.

  The present invention has been made in view of the above points, and an object of the present invention is to shorten a protruding length of a camshaft from a bearing portion and to reduce a size of a driven gear fitted to an end portion of the camshaft to be close to the bearing portion. The point is to provide an internal combustion engine capable of achieving the above.

In order to achieve the above object, the internal combustion engine according to the present invention,
The intake side camshaft (42) and the exhaust side camshaft (52) are equipped with a DOHC structure valve mechanism that is rotatably supported.
The intake side driven gear (47) and the exhaust side driven gear are respectively attached to the ends of the intake side camshaft (42) and the exhaust side camshaft (52) that penetrate the bearing wall (3U) and the camshaft holder (33). (57) is fitted,
An idle gear (61) that meshes with both the intake side driven gear (47) and the exhaust side driven gear (57) is rotatably supported by a support shaft (65) provided in the cylinder head (3).
An idle chain sprocket (62) is provided adjacent to the bearing wall (3U) side axially inside coaxially with the idle gear (61),
A cam chain (66) is bridged between the idle chain sprocket (62) and the drive chain sprocket (67) fitted to the crankshaft (10),
In an internal combustion engine in which the power of the crankshaft (10) is transmitted to the intake side camshaft (42) and the exhaust side camshaft (52),
The idle chain sprocket (62) is provided at a position that axially overlaps the bearing portion (3UA) of the bearing wall (3U) and the camshaft holder (33),
The intake side camshaft (42) and the exhaust side camshaft (52) are axially supported by the bearing portion (3UA) of the bearing wall (3U) at the same axial position as the idle chain sprocket (62). The camshaft holder (33) is fastened and attached to the bearing portion (3UA) of the bearing wall (3U) by fastening bolts (38a, 38b, 38c, 38d),
Of the fastening bolts (38a, 38b, 38c, 38d), the fastening bolts (38a, 38d) arranged at the end of the camshaft holder (33) are located on both sides of the idle chain sprocket (62). Fasten the fastening parts (33a, 33d) of
The bearing wall (3U) and the camshaft holder (33) have a bulging portion (3UB, 3UB, which bulges axially inward between the intake side camshaft (42) and the exhaust side camshaft (52). 33B),
A cylindrical member that is fitted to the outer circumference of the intake-side camshaft (42) such that relative rotation is prohibited and is slidable in the axial direction, and a plurality of cam lobes (43A, 43B) having different cam profiles are provided on the outer circumferential surface. An intake side cam carrier (43) having a lead groove cylindrical portion (43D) formed adjacent to each other in the axial direction and having a lead groove (44) with which a switching pin (73, 74) engages,
A cylindrical member that is fitted to the outer circumference of the exhaust side camshaft (52) such that relative rotation is prohibited and is slidable in the axial direction, and a plurality of cam lobes (53A, 53B) having different cam profiles are provided on the outer circumferential surface. An exhaust side cam carrier (53) having lead groove cylindrical portions (53D, 53E) formed adjacent to each other in the axial direction and having lead grooves (54, 55) with which the switching pins (83, 84) engage is formed. ) And
The bulging portion (3UB, 33B), the intake side cam carrier (43) and the exhaust side cam carrier (53) at least one of the lead groove cylindrical portion (43D), the axial position is the same. To do.

  According to this configuration, the idle chain sprocket (62) is provided at a position that axially overlaps the bearing portion (3UA) of the bearing wall (3U) and the camshaft holder (33), so that the idle gear is axially supported by the bearing. The intake side driven gear and the exhaust side driven gear that mesh with the idle gear can also be brought close to the bearing part, and the ends of the intake side camshaft and the exhaust side camshaft with the protruding length from the bearing part shortened The internal combustion engine can be fitted in the portion and disposed, and the axial width of the internal combustion engine can be suppressed to a small size, so that the internal combustion engine can be downsized.

According to this configuration, among the fastening bolts (38a, 38b, 38c, 38d), the fastening bolts (38a, 38d) arranged at the end portion of the camshaft holder (33) have the idle chain sprocket (62). Since the fastening parts (33a, 33d) on both sides are fastened with being sandwiched between them, the outer fastening bolts that are at the same position in the axial direction as the idle chain sprocket do not protrude upwards while avoiding the idle chain sprocket and By being located on both sides, it is possible to prevent the internal combustion engine from increasing in size without the upper portion of the cylinder head of the internal combustion engine projecting upward.
Since the bulging portion has the same axial position as the lead groove cylindrical portion of at least one of the intake-side cam carrier and the exhaust-side cam carrier, the bulging portion has a bulging bearing wall between the intake-side camshaft and the exhaust-side camshaft. The bulging part of the camshaft holder has the same axial position as the lead groove cylindrical part, so that the intake-side cam carrier and the exhaust-side cam carrier sandwiching the bulging part do not interfere with the cam lobe as much as possible. Can be brought closer to each other to reduce the size of the internal combustion engine.

In the above configuration,
At least one fastening bolt inside the fastening bolts (38a, 38b, 38c, 38d) may fasten a fastening portion provided on the bulging portion.

  According to this configuration, the bearing wall and the camshaft holder have a bulging portion that bulges inward in the axial direction between the intake side camshaft and the exhaust side camshaft, and the fastening bolts (38a, 38b, 38c, At least one fastening bolt on the inner side of 38d) fastens the fastening portion provided on the bulge portion, so the inner fastening bolt uses the space between the intake side camshaft and the exhaust side camshaft. The swelling bearing wall and the swelling portion of the camshaft holder can be fastened at a fastening part that avoids the idle chain sprocket in the axial direction, and the camshaft holder can be mounted compactly without increasing the size of the internal combustion engine. be able to.

In the above configuration,
A cam switching mechanism that switches the cam by moving the intake side cam carrier and the exhaust side cam carrier respectively by advancing and retracting the switching pin in the lead groove so that the switching pin can be engaged and disengaged,
The outer diameter of the lead groove cylindrical portion in which the lead groove is formed may be smaller than the outer diameter of the basic circle of the same diameter of the plurality of cam lobes.

According to the present invention, since the bearing portion of the bearing wall and the camshaft holder are provided at the same axial position as the idle chain sprocket on the bearing wall side axially inward of the idle gear, the idle gear can be brought closer to the bearing portion in the axial direction. The driven gear on the intake side and the driven gear on the exhaust side that mesh with this idle gear are also brought close to the bearing part, and are fitted on the respective ends of the intake side camshaft and the exhaust side camshaft with the protruding length from the bearing part shortened. The internal combustion engine can be miniaturized by suppressing the axial width of the internal combustion engine.
Since the bulging portion has the same axial position as the lead groove cylindrical portion of at least one of the intake-side cam carrier and the exhaust-side cam carrier, the bulging portion has a bulging bearing wall between the intake-side camshaft and the exhaust-side camshaft. The bulging part of the camshaft holder has the same axial position as the lead groove cylindrical part, so that the intake-side cam carrier and the exhaust-side cam carrier sandwiching the bulging part do not interfere with the cam lobe as much as possible. Can be brought closer to each other to reduce the size of the internal combustion engine.

1 is a right side view of an internal combustion engine equipped with a variable valve operating device according to a first embodiment of the present invention. It is a left side view which removed a partial cover of the internal combustion engine. FIG. 3 is a left side view of the internal combustion engine, in which a part of the internal combustion engine is omitted and a part of the valve is shown in section. It is a top view which removed the cylinder head cover and looked at the cylinder head from the upper part. It is a top view which removed the camshaft holder and looked at the same cylinder head from the above. Further, the cam shaft is removed together with the cam carrier, and the cylinder head is viewed from above. FIG. 7 is a sectional view taken along the line VII-VII in FIG. 4. FIG. 9 is a cross-sectional view taken along the line VIII-VIII in FIG. 4 with a cylinder head cover added. FIG. 9 is a sectional view taken along the line IX-IX in FIG. 4 with a cylinder head cover added. FIG. 3 is a sectional view taken along line XX in FIG. 2. It is a perspective view showing only main elements of an intake side cam switching mechanism and an exhaust side cam switching mechanism. It is a perspective view of a switching pin. It is an exploded perspective view of an intake side switching drive shaft and a first switching pin. It is a perspective view which attached the 1st switching pin and the 2nd switching pin to the intake side switching drive shaft. It is a perspective view which attached the 1st switching pin to the exhaust side switching drive shaft. It is explanatory drawing which showed the operation process of the main member of the intake side cam switching mechanism in order sequentially over time. It is explanatory drawing which showed the operation process of the main member of the exhaust side cam switching mechanism sequentially in order.

Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. 1 to 17.
An internal combustion engine E equipped with the variable valve operating device 40 according to the present embodiment is a water-cooled single-cylinder 4-stroke internal combustion engine, and is used in a motorcycle (not shown) equipped with a 4-valve DOHC valve operating mechanism. It will be installed.
In the description of the present specification, the front, rear, left, and right directions are in accordance with the normal standard in which the straight direction of the motorcycle is the front, and in the drawings, FR is the front, RR is the rear, LH is the left, RH indicates the right side.

The internal combustion engine E is mounted horizontally on a vehicle with the crankshaft 10 oriented in the vehicle width direction (left-right direction).
The crankcase 1 which pivotally supports the crankshaft 10 oriented in the left-right direction forms a crank chamber 1c in which the crankshaft 10 is arranged, and a transmission M is provided behind the crank chamber 1c with reference to FIG. Is formed, and an oil pan chamber 1o for storing oil is integrally formed below the crank chamber 1c by a substantially horizontal partition wall 1h.

  Referring to FIGS. 1 to 3, an internal combustion engine E includes a cylinder block 2 having one cylinder 2a on a crank chamber 1c of the crankcase 1, and a cylinder block 2 coupled to the upper portion of the cylinder block 2 via a gasket. And a cylinder head cover 4 that covers the upper portion of the cylinder head 3.

The cylinder axis Lc, which is the center axis of the cylinder 2a of the cylinder block 2, is slightly inclined rearward, and the cylinder block 2, the cylinder head 3, and the cylinder head cover 4 which are stacked on the crankcase 1 are slightly rearward from the crankcase 1. It extends upward in a tilted position.
An oil pan 5 that forms the oil pan chamber 1o extends below the crankcase 1.

  In the mission chamber 1m of the crankcase 1, a main shaft 11 and a countershaft 12 of the transmission M are arranged in parallel with the crankshaft 10 in a horizontal direction (see FIG. 3). Reference numeral 12 is an output shaft that penetrates the crankcase 1 to the left and projects to the outside.

  The transmission M disposed in the mission chamber 1m behind the crank chamber 1c includes a main shaft 11 and a counter shaft 12 provided with a main gear group 11g and a counter gear group 12g, respectively, and a shift operated by a shift operation mechanism. A gear shift mechanism 15 having a drum 16 and shift forks 17a, 17b, 17c is provided (see FIG. 3).

  Referring to FIG. 3, a piston 20 and a crankshaft 10 which reciprocate in a cylinder 2a of a cylinder block 2 are connected to respective piston pins 20p and crankpins 10p by connecting rods 21 supported at both ends to form a crank. It constitutes the mechanism.

The internal combustion engine E is equipped with a variable valve operating device 40 having a four-valve system and a DOHC structure.
Referring to FIG. 3, a combustion chamber 30 is formed in the cylinder head 3 so as to face the top surface of the piston 20 in the cylinder axis direction so as to correspond to the cylinder 2a. From the combustion chamber 30, an intake port 31i is provided. Two of them are curved forward and extend obliquely upward, and two of the exhaust ports 31e are curved and extend rearward.

The two intake ports 31i, 31i are joined together on the upstream side, and a throttle body 22 is interposed in an intake passage that is an extension of the intake port, and the upstream side of the intake passage of the throttle body 22 is open.
A spark plug 23 is attached to the center of the ceiling wall of the combustion chamber 30 with its tip facing the combustion chamber 30.

  The intake valve 41 and the exhaust valve 51, which are slidably supported by the valve guides 32i and 32e integrally fitted to the cylinder head 3, are driven by a variable valve operating device 40 provided in the internal combustion engine E, and intake air intake is performed. The intake opening of the port 31i and the exhaust opening of the exhaust port 31e are opened and closed in synchronization with the rotation of the crankshaft 10.

The variable valve operating device 40 is provided in a valve operating chamber 3c formed by the cylinder head 3 and the cylinder head cover 4.
Referring to FIG. 6, which is a top view of the cylinder head 3 with a part of the variable valve operating device 40 removed, the cylinder head 3 includes front and rear front side walls 3Fr, rear side walls 3Rr, and left and right left side walls 3L. The right side wall 3R forms a rectangular shape, and the bearing wall 3U formed in parallel with the left side wall 3L partitions the valve operating chamber 3c to form a gear chamber 3g on the left side.
The valve operating chamber 3c is located above the combustion chamber 30 and is partitioned into left and right chambers by the bearing wall 3V.

  A bearing concave surface 3Ui, 3Ue forming a semi-circular surface is formed on the upper end surface of the bearing wall 3U partitioning the gear chamber 3g, and a semi-circular arc is formed on the upper end surface of the bearing wall 3V partitioning the valve operating chamber 3c. The bearing concave surfaces 3Vi and 3Ve forming the surface are formed, and the plug fitting insertion cylinder portion 3Vp into which the ignition plug 23 is fitted is formed in the center.

  A pair of left and right intake valves 41, 41 are arranged in the left-right direction, and an intake-side camshaft 42 and a pair of left-right exhaust valves 51, 51 are arranged in the left-right direction. The exhaust side camshaft 52 is rotatably supported by being sandwiched between bearing walls 3U and 3V perpendicular to the axial direction (left-right direction) of the cylinder head 3 and camshaft holders 33 and 34 (Fig. 4, Fig. 4). 10).

Referring to FIGS. 5 and 10, the intake side camshaft 42 has a bearing portion 42B whose left end portion has an enlarged diameter, and flange portions 42A and 42C are formed on the left and right of the bearing portion 42B.
A spline shaft portion 42D having spline external teeth formed on the outer peripheral surface thereof extends to the right of the right flange portion 42C.

An oil supply passage 42h is bored along the central axis of the intake side camshaft 42 from the right end surface to the inside of the bearing portion 42B through the inside of the spline shaft portion 42D, and the emission from the left end portion of the oil supply passage 42h. Is formed to the outer peripheral surface of the bearing portion 42B in the axial direction, and in the spline shaft portion 42D, there are three cam axial oil passage holes 42hb and bearing hydraulic passage holes 42hc in the radial direction from the lubrication passage 42h at three axial positions. The cam communication oil hole 42hb is bored.
The left cam communicating oil hole 42hb, the center bearing communicating oil hole 42hc, and the right cam communicating oil hole 42hb are formed on the outer peripheral surface of the spline shaft portion 42D so as to surround the three cam outer peripheral grooves 42bv and the bearing outer periphery. The groove 42cv and the cam outer peripheral groove 42bv are opened (see FIG. 10).
A plug member 45 is press-fitted and closed at the right end of the oil supply passage 42h.

As shown in FIGS. 6 and 7, inner peripheral oil grooves 3Uiv, 3Uev are formed in the bearing concave surfaces 3Ui, 3Ue that support the intake side camshaft 42 and the exhaust side camshaft 52 in the bearing portion 3UA of the cylinder head 3. Has been done.
On the other hand, referring to FIG. 7, the camshaft holder 33 has a common oil passage 33s formed by drilling in the front-rear direction along the upper surface of the holder. The common oil passage 33s is formed on the intake side camshaft 42 and the exhaust side. It passes in common above the bearing concave surfaces 33i and 33e for bearing the camshaft 52.
The common oil passage 33s passes through a bolt hole of a fastening bolt 38d described later on the way.

Branch oil passages 33it and 33et branched from the common oil passage 33s are bored toward the mating surface with the bearing portion 3UA of the cylinder head 3 (see FIG. 7).
As shown in FIG. 7, the branch oil passage 33it communicates with the inner peripheral oil groove 3Uiv opened to the rear side of the bearing concave surface 3Ui on the cylinder head 3 side, and the branch oil passage 33et has the bearing concave surface on the cylinder head 3 side. It communicates with the inner peripheral oil groove 3Uev opened on the front side of 3Ue.
The common oil passage 33s communicates with the vertical oil passage 33r at the rear end, and the vertical oil passage 33r communicates with the vertical oil passage 3Ur on the bearing wall 3U side of the cylinder head 3.

  Therefore, the oil that has passed through the vertical oil passage 3Ur of the cylinder head 3 flows into the common oil passage 33s through the vertical oil passage 33r on the camshaft holder 33 side, and is distributed from the common oil passage 33s to the branch oil passages 33it and 33et. Then, the oil is supplied to the front and rear inner circumferential oil grooves 3Uiv, 3Uev to lubricate the bearings of the intake side camshaft 42 and the exhaust side camshaft 52.

Further, the oil supply communication hole 42ha of the bearing receiving portion 42B of the intake side camshaft 42 is opened to the inner peripheral oil groove 3Uiv (see FIGS. 7 and 10), and oil is supplied from the inner peripheral oil groove 3Uiv to the oil supply communication hole 42ha. It is supplied to the oil supply passage 42h of the intake side camshaft 42 through.
Similarly, the oil supply communicating hole 52ha of the bearing receiving portion 52B of the exhaust side camshaft 52 is open to the inner peripheral oil groove 3Uev (see FIG. 7), and the oil passes from the inner peripheral oil groove 3Uev to the oil supplying communication hole 52ha. It is supplied to the oil supply passage 52h of the exhaust side camshaft 52.

Then, referring to FIG. 10, the oil supplied to the oil supply passage 42h from the oil supply communication hole 42ha of the bearing receiving portion 42B of the intake side camshaft 42 is the same as that of the cam communication oil hole 42hb, the bearing communication oil hole 42hc, and the cam communication oil. It is discharged from the hole 42hb to the outer peripheral surface of the spline shaft portion 42D.
The oil supplied to the oil supply passage 52h from the oil supply communication hole 52ha of the bearing receiving portion 52B of the exhaust side camshaft 52 is discharged to the outer peripheral surface of the spline shaft portion 52D from a similar communication oil hole (not shown).

The intake side cam carrier 43, which is a cylindrical member, is spline-fitted to the spline shaft portion 42D of the intake side cam shaft 42.
Therefore, the intake side cam carrier 43 is fitted to the intake side cam shaft 42 so as to be slidable in the axial direction while being prohibited from relative rotation.
The oil discharged from the cam communication oil hole 42hb, the bearing communication oil hole 42hc, and the cam communication oil hole 42hb is supplied to the spline fitting portion (see FIG. 10).

As shown in FIG. 10, on the right side surface of the right side flange portion 42C of the bearing portion 42B, which is the expanded diameter portion of the intake side camshaft 42, the left end portion of the intake side cam carrier 43 comes into contact with, A recess 42Ch into which the left end can be inserted is formed.
The recessed portion 42Ch formed on the right side surface of the bearing receiving portion 42B of the intake side camshaft 42 secures a necessary movement space of the intake side cam carrier 43, and the bearing receiving portion 42B of the intake side camshaft 42 is moved to the intake side cam carrier. The intake side camshaft 42 can be set shorter by approaching the 43 side.

In the intake side cam carrier 43, a pair of first cam lobes 43A and second cam lobes 43B having different cam profiles on the outer peripheral surface are axially left and right adjacent to each other, and a bearing cylindrical portion 43C having a predetermined width is axially sandwiched therebetween. The left and right sides are formed one by one.
The first cam lobe 43A and the second cam lobe 43B which are adjacent to each other have the same outer diameters of the basic circles of the cam profile and are in the same circumferential position (see FIG. 8).

5 and 10, the intake-side cam carrier 43 is arranged so that the lead groove 44 circulates to the left of the left first cam lobe 43A in the set of the left first cam lobe 43A and the second cam lobe 43B. It has the formed lead groove cylindrical portion 43D, and has the right end cylindrical portion 43E on the right side of the right second cam lobe 43B in the set of the right first cam lobe 43A and the second cam lobe 43B.
The outer diameter of the lead groove cylindrical portion 43D is smaller than the outer diameter of the basic circle of the same diameter of the first cam lobe 43A and the second cam lobe 43B (see FIG. 10).

  The lead groove 44 of the lead groove cylindrical portion 43D is formed with an annular lead groove 44c that makes an annular turn in a circumferential direction at a predetermined position in the axial direction, and branches left and right from the annular lead groove 44c for a predetermined distance in the left and right directions in the axial direction. A left shift lead groove 44l and a right shift lead groove 44r are spirally formed up to the separated positions (see FIGS. 4 and 10).

The left shift lead groove 44l is formed near the left end surface of the intake side cam carrier 43.
Therefore, the end portion of the intake-side cam carrier 43 can be made as short as possible to reduce the axial width of the intake-side cam carrier 43 itself.

  As shown in FIG. 10, when the left end portion of the intake side cam carrier 43 is inserted into the recess 42Ch formed on the right side surface of the bearing portion 42B of the intake side cam shaft 42, the left end surface of the intake side cam carrier 43 is inserted. Although a part of the left shift lead groove 44l formed in the vicinity of the left shift lead groove 44l is also inserted into the recess 42Ch, the other part of the left shift lead groove 44l is exposed without entering the recess 42Ch. Engagement of the switching pin 73 does not hinder the cam switching.

Referring to FIG. 10, bearing cylindrical portion 43C of intake side cam carrier 43 is formed with bearing oil supply holes 43Ca and 43Cb which communicate with the inside and outside of the cylinder at two axial positions.
Further, cam oil supply holes 43Ah and 43Bh are formed in the first cam lobe 43A and the second cam lobe 43B so as to communicate from the inner side to the outer side of the cam surface of the base circle (see FIGS. 9 and 10).

The intake side cam carrier 43 and the exhaust side cam carrier 53 rotate clockwise in the side view shown in FIG. 9, and the cam surface of the rotating intake side cam carrier 43 of the second cam lobe 43B shown in FIG. 9 will be described later. The intake rocker arm 72 is slidably contacted to swing the intake rocker arm 72 to operate the intake valve 41.
On the cam surface of the cam lobe of the second cam lobe 43B, there is a side where the cam surface pressure first comes into sliding contact with the intake rocker arm 72 and a side where the cam surface pressure comes into sliding contact with the intake rocker arm 72 and then falls. The cam oiling hole 43Bh of the second cam lobe 43B is opened at a position closer to the side where the cam surface pressure rises than the side where the cam surface pressure of the cam crest falls on the cam surface of the base circle of the second cam lobe 43B. Has been drilled.

Similarly, the cam oil supply hole 43Ah of the first cam lobe 43A is also formed so as to open at a position close to the side where the cam surface pressure increases on the cam surface of the basic circle of the first cam lobe 43A.
The same applies to the cam oil supply holes in the first cam lobe 53A and the second cam lobe 53B of the exhaust side cam carrier 53.

A cap member 46 having a bottomed cylindrical shape is fitted and covered on the right end cylindrical portion 43E of the intake side cam carrier 43.
Further, the intake side driven gear 47 is coaxially fitted to the left side flange portion 42A of the intake side camshaft 42 from the left side and is integrally fastened by two screws 48, 48 (see FIG. 10).

  With reference to FIG. 10, the intake side cam carrier 43 is spline-fitted to the spline shaft portion 42D of the intake side cam shaft 42, and the right end cylindrical portion 43E of the intake side cam carrier 43 is covered with the cap member 46. The bearing portion 42B of the side camshaft 42 is rotatably supported by being sandwiched between the bearing concave surface 3Ui formed in the bearing wall 3U of the cylinder head 3 and the semicircular bearing concave surface 33i of the camshaft holder 33. The bearing cylindrical portion 43C of the intake side cam carrier 43 is rotatably supported by being sandwiched between the bearing concave surface 3Vi formed on the bearing wall 3V of the cylinder head 3 and the semi-circular bearing concave surface 34i of the camshaft holder 34. .

The intake-side camshaft 42 is axially positioned such that the left and right flange portions 42A and 42C of the bearing portion 42B sandwich the bearing wall 3U of the cylinder head 3 and the camshaft holder 33, and are attached to the left-side flange portion 42A. The driven gear 47 on the intake side is located in the gear chamber 3g.
The intake-side cam carrier 43, which is spline-fitted to the spline shaft portion 42D of the intake-side cam shaft 42 that is axially positioned and thus rotated, is movable in the axial direction while rotating with the intake-side cam shaft 42. is there.

  In the intake side cam carrier 43, since the bearing cylindrical portion 43C having a predetermined width in the axial direction is supported by the bearing wall 3V of the cylinder head 3 and the camshaft holder 34, the bearing wall 3V and the camshaft holder 34 are sandwiched to the left. The second cam lobe 43B which opposes and the first cam lobe 43A which opposes the right side contact the bearing wall 3V and the cam shaft holder 34, whereby the movement of the intake side cam carrier 43 in the axial direction is restricted (see FIG. 10).

With reference to FIG. 10, the oil in the oil supply passage 42h of the intake side camshaft 42 is supplied to the cam communicating oil hole 42hb, the bearing communicating oil hole 42hc, the cam communicating oil hole 42hb, the cam outer peripheral groove 42bv, the bearing outer peripheral groove 42cv, It is discharged into the cam outer peripheral groove 42bv to lubricate the spline fitting portion of the outer periphery of the spline shaft portion 42D with the intake side cam carrier 43, and the bearing communication oil hole 42hc of the bearing portion 42B of the intake side cam shaft 42, The bearing wall 3V and the cam shaft holder 34 are at the same axial position, and the bearing cylindrical portion 43C of the intake side cam carrier 43 that moves axially corresponding to the bearing communication oil hole 42hc has two bearing oil supply holes 43Ca. , 43Cb, one of the bearing oil supply holes 43Cb faces the bearing communication oil hole 42hc when the intake side cam carrier 43 is shifted to the left as shown in FIG. 5, and the other bearing oil supply hole 43Ca is communicated when the right shift is performed. Since it faces the oil hole 42hc, the bearing can be used during any shift. Oil can be supplied to the bearing concave surfaces 3Vi and 34i for lubrication through either the oil supply hole 43Ca or the bearing oil supply hole 43Cb.

In order to regulate and position the intake side cam carrier 43 in the axial direction, spherical engagement recesses are formed at the axial positions of the bearing oil supply holes 43Ca and 43Cb on the inner peripheral surface of the intake side cam carrier 43. Then, the engagement ball urged by the coil spring installed at the axial position of the bearing communication oil hole 42hc in the intake side camshaft 42 is protruded from the outer peripheral surface of the intake side camshaft 42 so as to be retractable, and The positioning may be performed by engaging with one of the engaging recesses.
The two engagement recesses and the engagement balls can be provided at any positions in the axial direction of the intake side cam carrier 43 and the intake side cam shaft 42 as long as the above positional relationship is maintained.

  Further, the cam communication oil holes 42hb, 42hb on both sides of the bearing communication oil hole 42hc of the intake side camshaft 42 are at the same axial positions as the intake valves 41, 41 (and intake rocker arms 72, 72 described later), When the intake side cam carrier 43 is shifted to the left, the second cam lobes 43B and 43B are in the same axial position (see FIG. 5), and when the intake side cam carrier 43 is shifted to the right, the first cam lobes 43A and 43A are in the same axial position. Become.

  Therefore, when the intake side cam carrier 43 shifts to the left, as shown in FIG. 10, the cam oil supply holes 43Bh, 43Bh of the second cam lobes 43B, 43B become the cam communication oil holes 42hb, 42hb of the intake side camshaft 42. Opposingly, oil is supplied to the cam surfaces of the second cam lobes 43B, 43B to lubricate the sliding contact portions with the intake rocker arms 72, 72.

When the intake side cam carrier 43 shifts to the right, the cam oil supply holes 43Ah, 43Ah of the first cam lobes 43A, 43A face the cam communication oil holes 42hb, 42hb of the intake side cam shaft 42, and the first cam lobes 43A, 43A of the first cam lobes 43A, 43A move. Oil is supplied to the cam surface to lubricate the sliding contact portion with the intake rocker arms 72, 72.
In this way, oil can be supplied to the sliding contact portion between the cam lobes 43A and 43B and the intake rocker arm 72 for lubrication during either the left or right shift.

  On the other hand, the exhaust side cam shaft 52 has the same shape as the intake side cam shaft 42, and a left side flange portion 52A, a bearing portion 52B, a right side flange portion 52C, and a spline shaft portion 52D are formed in order (FIG. 5).

The exhaust side cam carrier 53, which is spline-fitted to the spline shaft portion 52D of the exhaust side cam shaft 52, is similar to the intake side cam carrier 43 in that it has a pair of first cam lobes 53A having a different cam profile on the outer peripheral surface. Two cam lobes 53B that are adjacent to each other in the axial direction are formed on the left and right, respectively, with a bearing cylindrical portion 53C having a predetermined width interposed therebetween.
The first cam lobe 53A and the second cam lobe 53B adjacent to each other have the same outer diameter of the basic circle of the cam profile.

However, with reference to FIG. 11, the exhaust side cam carrier 53 is different from the intake side cam carrier 43 in that the lead groove is formed in two places, and the left side and the left side of the first cam lobe 53A of the left group are formed. It has a lead groove cylindrical portion 53D formed so that the lead groove 54 circulates, and a lead groove cylindrical portion 53E formed so that the right lead groove 55 circulates on the right side of the right side second cam lobe 53B. The right end cylindrical portion 53F is provided on the right side of the lead groove cylindrical portion 53E.
The outer diameters of the lead groove cylindrical portions 53D and 53E are smaller than the outer diameter of the basic circle of the same diameter of the first cam lobe 53A and the second cam lobe 53B.

4 and 5, the lead groove 54 of the left lead groove cylindrical portion 53D is formed with an annular lead groove 54c that makes one round in the circumferential direction at a predetermined axial position close to the left end surface of the exhaust side cam carrier 53. The right shift lead groove 54r is formed in a spiral shape to branch to the right from the annular lead groove 54c and to a position separated by a predetermined distance in the axial right direction.
The lead groove 55 of the right lead groove cylindrical portion 53E is formed with an annular lead groove 55c that makes one round in the circumferential direction at a predetermined axial position, and is branched to the left from the annular lead groove 55c and is located at a predetermined distance leftward in the axial direction. The left shift lead groove 55l is spirally formed.

A cap member 56 having a bottomed cylindrical shape is fitted and covered on the right end cylindrical portion 53F (see FIG. 11) of the exhaust side cam carrier 53 (see FIG. 5).
Further, an exhaust side driven gear 57 is coaxially fitted to the left side flange portion 52A of the exhaust side cam shaft 52 from the left side and is integrally fastened by two screws 58, 58 (see FIGS. 4 and 5). .

  Referring to FIG. 5, in a state in which the exhaust side cam carrier 53 is spline-fitted to the spline shaft portion 52D of the exhaust side cam shaft 52, and the right end cylindrical portion 53F of the exhaust side cam carrier 53 is covered with the cap member 56. 6, the bearing receiving portion 52B of the exhaust side camshaft 52 is rotatably supported by being sandwiched between the bearing concave surface 3Ue formed on the bearing wall 3U of the cylinder head 3 and the semicircular bearing concave surface of the camshaft holder 33. In addition, the bearing cylindrical portion 53C of the exhaust side cam carrier 53 is rotatably supported by being sandwiched between the bearing concave surface 3Ve formed on the bearing wall 3V of the cylinder head 3 and the semicircular bearing concave surface of the camshaft holder 34. Supported (see Figure 4).

The exhaust side camshaft 52 is axially positioned such that the left and right flange portions 52A and 52C of the bearing receiving portion 52B sandwich the bearing wall 3U of the cylinder head 3 and the camshaft holder 33, and are attached to the left flange portion 52A. The driven gear 57 on the exhaust side is located in the gear chamber 3g.
The exhaust side cam carrier 53, which is spline-fitted to the spline shaft portion 52D of the exhaust side cam shaft 52 which is axially positioned and thus rotated, is movable in the axial direction while rotating together with the exhaust side cam shaft 52. is there.

  In the exhaust side cam carrier 53, the bearing cylindrical portion 53C having a predetermined width in the axial direction is supported by the bearing wall 3V of the cylinder head 3 and the camshaft holder 34, so that the bearing wall 3V and the camshaft holder 34 are sandwiched to the left. The second cam lobe 53B that opposes and the first cam lobe 53A that opposes the right side contact the bearing wall 3V and the cam shaft holder 34, so that the movement of the exhaust side cam carrier 53 in the axial direction is restricted.

  The oil supply path for lubricating the spline fitting portion of the exhaust side cam shaft 52 and the exhaust side cam carrier 53 and other bearings is substantially the same as the structure of the intake side cam shaft 42 and the intake side cam carrier 43.

  An intake side driven gear 47 attached to the left side flange portion 42A of the intake side camshaft 42 and an exhaust side driven gear 57 attached to the left side flange portion 52A of the exhaust side camshaft 52 are arranged side by side in the gear chamber 3g. It is set up.

As shown in FIG. 2, an idle gear 61 that meshes with both the intake-side driven gear 47 and the exhaust-side driven gear 57 of the same diameter before and after this is provided below them.
The idle gear 61 is a gear having a larger diameter than the intake side driven gear 47 and the exhaust side driven gear 57, and as shown in FIG. 10, a gear chamber 3g is provided between the left side wall 3L of the cylinder head 3 and the bearing wall 3U. It is rotatably supported via a bearing 63 on a cylindrical support shaft 65 that extends through the shaft.

The cylindrical support shaft 65 penetrates the left side wall 3L and is fixed to the bearing wall 3U by bolts 64.
The end face of the large diameter portion of the cylindrical support shaft 65 is fixed by sandwiching the inner race of the bearing 63 with the bearing wall 3U via the collar member 65a and tightening with the bolt 64.

Referring to FIG. 10, the idle gear 61 has a cylindrical boss portion 61b that fits into the outer race of the bearing 63 and protrudes to the right. The idle chain sprocket 62 is fitted around the outer periphery of the cylindrical boss portion 61b. ing.
The idle chain sprocket 62 has a large outer diameter that is substantially the same as the idle gear 61.

  This large-diameter idle chain sprocket 62, as shown in FIGS. 7 and 10, has an upper end of a bearing wall 3U that supports a bearing portion 42B of the intake camshaft 42 and a bearing portion 52B of the exhaust camshaft 52. Of the bearing concave surfaces 3Ui, 3Ue of the bearing portion 3UA at the same axial direction (horizontal direction) and below the bearing portion 3UA.

  Referring to FIG. 4, the bearing concave portions 3Ui and 3Ue of the bearing portion 3UA of the cylinder head 3 are provided with the bearing portion 42B of the intake side camshaft 42 and the bearing portion 52B of the exhaust side camshaft 52 with the bearing concave surfaces 33i and 33e. In the camshaft holder 33 which is supported by sandwiching it, fastening portions 33a, 33b having bolt holes on both sides of the intake side camshaft 42 are fastened by fastening bolts 38a, 38b, and the camshaft holder 42 is sandwiched by the exhaust side camshaft 52. Fastening parts 33c, 33d having bolt holes on both sides are fastened by fastening bolts 38c, 38d.

  Since the large diameter idle chain sprocket 62 is arranged below the bearing portion 3UA of the cylinder head 3, the two fastening bolts 38a, 38d outside the front and rear of the four fastening bolts 38a, 38b, 38c, 38d are idle. The chain sprocket 62 is sandwiched in between to fasten the fastening portions 33a and 33d on both sides (see FIGS. 4 and 7).

  Further, as shown in FIGS. 4 and 5, the bearing wall 3U of the cylinder head 3 and the camshaft holder 33 are axially inside (right side) between the intake side camshaft 42 and the exhaust side camshaft 52. Bulging parts 3UB and 33B are formed.

The bulging portions 3UB, 33B bulge to a position avoiding the lower idle chain sprocket 62 inward in the axial direction (right side), and as shown in FIGS. 4 and 5, the lead of the intake side cam carrier 43. The groove cylindrical portion 43D and the groove cylindrical portion 43D have the same axial position and are provided close to each other in the front-rear direction.
Of the four fastening bolts 38a, 38b, 38c, 38d, the inner two fastening bolts 38b, 38c fasten the fastening portions 33b, 33c provided on the bulging portion 33B (see FIGS. 4 and 7). ).

Referring to FIG. 4, the camshaft holder 34, which axially supports the supported cylindrical portion 43C of the intake side cam carrier 43 and the supported cylindrical portion 53C of the exhaust side cam carrier 53 between the bearing wall 3V, is The front and rear sides are fastened with fastening bolts 39a and 39b with the bearing cylindrical portion 43C sandwiched therebetween, and the front and rear sides are fastened with fastening bolts 39c and 39d sandwiched with the supported cylindrical portion 53C.
At the center of the camshaft holder 34, a plug fitting cylindrical portion 34p that is connected to the plug fitting cylindrical portion 3Vp of the bearing wall 3V is formed (see FIG. 4).

Referring to FIG. 2, a cam chain 66 is wound around a large-diameter idle chain sprocket 62, and on the other hand, the cam chain 66 is mounted on a small-diameter drive chain sprocket 67 fitted to the lower crankshaft 10. It is wrapped around.
The cam chain 66 wound around the idle chain sprocket 62 and the drive chain sprocket 67 is given tension by the cam chain tensioner guide 68, and is rotated by being guided by the cam chain guide 69 (see FIG. 2).

  Therefore, the rotation of the crankshaft 10 is transmitted to the idle chain sprocket 62 via the cam chain 66 to rotate the idle chain sprocket 62 together with the idle gear 61, and the rotation of the idle gear 61 meshes with the idle gear 61 on the intake side. Since the driven gear 47 and the exhaust side driven gear 57 are rotated, the intake side driven gear 47 rotates integrally with the intake side cam shaft 42, and the exhaust side driven gear 57 rotates integrally with the exhaust side cam shaft 52.

FIG. 11 is a perspective view showing only main elements of the intake side cam switching mechanism 70 and the exhaust side cam switching mechanism 80 of the variable valve operating device 40.
An intake-side cam carrier 43 and an exhaust-side cam carrier 53 are spline-fitted to an intake-side camshaft 42 and an exhaust-side camshaft 52, which rotate in synchronization with the crankshaft 10.

  The intake-side switching drive shaft 71 of the intake-side cam switching mechanism 70 is arranged parallel to the intake-side camshaft 42 diagonally below and rearward of the intake-side camshaft 42, and the exhaust-side camshaft 52 is located diagonally below and rearward of the exhaust-side camshaft 52. The exhaust side switching drive shaft 81 of the cam switching mechanism 80 is arranged in parallel with the exhaust side cam shaft 52.

The intake side switching drive shaft 71 and the exhaust side switching drive shaft 81 are supported by the cylinder head 3.
With reference to FIG. 6, a tubular portion 3A oriented in the left-right direction in the valve operating chamber 3c of the cylinder head 3 is located at a position slightly forward of the center and extends straight from the bearing wall 3U through the bearing wall 3V to the right side wall 3R. Has been formed.

Further, a cylindrical portion 3B oriented in the left-right direction in the valve operating chamber 3c of the cylinder head 3 is formed on the inner surface of the rear side wall 3Rr in a straight line from the bearing wall 3U through the bearing wall 3V to the right side wall 3R.
The intake side switching drive shaft 71 is slidably inserted in the axial hole of the tubular portion 3A, and the exhaust side switching drive shaft 81 is axially slidably inserted in the axial hole of the tubular portion 3B. Be done.

At the positions on both sides of the bearing wall 3V in the tubular portion 3A, two positions corresponding to the left and right intake valves 41, 41 are missing and the intake side switching drive shaft 71 is exposed. The intake rocker arms 72, 72 are pivotally supported on the exposed portion of 71 so as to be swingable (see FIGS. 7 and 8).
That is, the intake side switching drive shaft 71 also serves as a rocker arm shaft.

Referring to FIG. 11, the tip of the intake rocker arm 72 abuts the upper end of the intake valve 41, and the curved upper end surface of the intake rocker arm 72 is moved by the first cam lobe 43A or the second cam lobe 43A by the movement of the intake side cam carrier 43. One of the cam lobes 43B is in sliding contact.
Therefore, when the intake-side cam carrier 43 rotates, either the first cam lobe 43A or the second cam lobe 43B swings the intake rocker arm 72 according to the profile and presses the intake valve 41 to press the intake valve opening of the combustion chamber 30. open.

Similarly, two positions corresponding to the left and right exhaust valves 51, 51 are missing at positions on both sides of the bearing wall 3V in the tubular portion 3B, and the exhaust side switching drive shaft 81 is exposed. An exhaust rocker arm 82 is swingably supported on the exposed portion of the switching drive shaft 81 (see FIG. 6).
That is, the exhaust side switching drive shaft 81 also serves as a rocker arm shaft.

Referring to FIG. 11, the tip of the exhaust rocker arm 82 contacts the upper end of the exhaust valve 51, and the curved upper end surface of the exhaust rocker arm 82 is moved by the first cam lobe 53A or the second cam lobe 53A by the movement of the exhaust side cam carrier 53. One of the cam lobes 53B makes sliding contact.
Therefore, when the exhaust side cam carrier 53 rotates, either the first cam lobe 53A or the second cam lobe 53B swings the exhaust rocker arm 82 according to the profile and presses the exhaust valve 51 to press the exhaust valve opening of the combustion chamber 30. open.

With reference to FIGS. 5 and 6, two cylindrical boss portions that are adjacent to the left and right at a position near the bearing wall 3U of the tubular portion 3A and at a position corresponding to the lead groove cylindrical portion 43D of the intake side cam carrier 43. 3As and 3As are formed so as to project toward the lead groove cylindrical portion 43D.
The inner hole of the cylindrical boss portion 3As penetrates the tubular portion 3A.
A first switching pin 73 and a second switching pin 74 are slidably fitted into the inner holes of the left and right cylindrical boss portions 3As, 3As, respectively.

  Referring to FIG. 8, the tip opening portion of the cylindrical boss portion 3As from which the first switching pin 73 (and the second switching pin 74) projects is a circle of the maximum diameter of the cam lobes of the first cam lobe 43A and the second cam lobe 43B. In the axial direction (FIG. 8).

That is, the maximum diameter circle of the first cam lobe 43A having a small cam lobe overlaps with the tip opening of the cylindrical boss portion 3As.
Therefore, the intake side switching drive shaft 71 can be arranged as close as possible to the intake side cam shaft 42, and the internal combustion engine E can be downsized.

With reference to FIG. 12, in the first switching pin 73, the distal end columnar portion 73a and the base end columnar portion 73b are connected by an intermediate connecting rod portion 73c in a straight line.
The outer diameter of the proximal cylindrical portion 73b is smaller than that of the distal cylindrical portion 73a.

Further, a reduced-diameter engagement end 73ae further projects from the tip cylindrical portion 73a.
An end surface of the base end cylindrical portion 73b on the side of the intermediate connecting rod portion 73c forms a conical conical end surface 73bt.
The end surface of the base end cylindrical portion 73b on the side of the intermediate connecting rod portion 73c may have a spherical shape.
The second switching pin 74 also has the same shape as the first switching pin 73.

On the other hand, in the intake side switching drive shaft 71, as shown in FIG. 13, a long hole 71a penetrating the axial center is formed on the left side, and a circular hole 71b penetrating the axial center is formed at the left end of the long hole 71a. Has been done.
The width of the long hole 71a is slightly larger than the diameter of the intermediate connecting rod portion 73c of the first switching pin 73, and the inner diameter of the circular hole 71b is slightly larger than the outer diameter of the proximal end cylindrical portion 73b, but the outside of the distal end cylindrical portion 73a. Smaller than diameter.

  Referring to FIG. 13, one opening end surface of the elongated hole 71a of the intake side switching drive shaft 71 is a flat surface 71Cp that is edged and extends linearly with inclination, and is recessed into a predetermined shape at a predetermined position on the way. A cam surface 71C composed of the formed concave curved surface 71Cv is configured.

The first switching pin 73 is slidably engaged with the intermediate connecting rod portion 73c through the elongated hole 71a of the intake side switching drive shaft 71 (see FIG. 14).
To assemble the first switching pin 73 to the intake side switching drive shaft 71, do the following.

  As shown in FIG. 13, a coil spring 75 is provided around the first switching pin 73. The coil spring 75 has an inner diameter larger than the outer diameter of the base end cylindrical portion 73b and an outer diameter outside the tip end cylindrical portion 73a. Since the diameter is smaller than the diameter, when the first switching pin 73 is inserted into the coil spring 75 from the base end cylindrical portion 73b side, the end surface of the tip end cylindrical portion 73a on the side of the intermediate connecting rod portion 73c abuts on the end portion of the coil spring 75.

  Then, the intake side switching drive shaft 71 is inserted into the shaft hole of the cylindrical portion 3A of the cylinder head 3, and the circular hole 71b is coaxial with the inner hole of the cylindrical boss portion 3As formed in the cylindrical portion 3A. Then, when the first switching pin 73 around which the coil spring 75 is provided is inserted into the hole inside the cylindrical boss portion 3As from the base end cylindrical portion 73b side, the coil spring 75 is inserted into the hole inside the cylindrical boss portion 3As together with the coil spring 75. The first switching pin 73 is slidably fitted (see FIG. 8), and the base end cylindrical portion 73b penetrates the circular hole 71b of the intake side switching drive shaft 71 inserted into the shaft hole of the tubular portion 3A. (See Figure 13).

  Even if the base end cylindrical portion 73b of the first switching pin 73 penetrates the circular hole 71b of the intake side switching drive shaft 71, the coil spring 75 cannot penetrate, and the end of the coil spring 75 is located at the opening end surface of the circular hole 71b. It abuts and is compressed between the end surface of the tip cylindrical portion 73a.

Since the intermediate connecting rod portion 73c of the first switching pin 73 is located at a position corresponding to the elongated hole 71a of the intake side switching drive shaft 71 with the base end columnar portion 73b penetrating the circular hole 71b, the intake side switching drive is performed. When the shaft 71 is moved to the left, the intermediate connecting rod portion 73c enters the elongated hole 71a with the coil spring 75 compressed.
Then, as shown in FIG. 14, in the first switching pin 73, the conical end surface 73bt of the base end cylindrical portion 73b is the opening end surface of the long hole 71a of the intake side switching drive shaft 71 due to the biasing force of the coil spring 75. The first switching pin 73 is assembled by being pressed and engaged with the surface 71C.

  As described above, in the first switching pin 73, the intermediate connecting rod portion 73c penetrates the elongated hole 71a of the intake side switching drive shaft 71 and is biased by the coil spring 75 so that the conical end surface 73bt of the base end cylindrical portion 73b is sucked. When the intake side switching drive shaft 71 moves in the axial direction, the cam surface 71C, which is the opening end surface of the elongated hole 71a of the side switching drive shaft 71, is assembled in a state where it is in the axial fixed position. The cam surface 71C with which the conical end surface 73bt of the base end cylindrical portion 73b of the first switching pin 73 that slides abuts slides and is guided by the shape of the cam surface 71C so that the first switching pin 73 is in a direction perpendicular to the axial direction. A linear cam mechanism Ca that moves forward and backward is configured.

  In the direct acting cam mechanism Ca, when the conical end surface 73bt of the first switching pin 73 contacts the flat surface 71Cp of the cam surface 71C of the intake side switching drive shaft 71, the first switching pin 73 is in the retracted position, When the intake side switching drive shaft 71 moves to bring the conical end surface 73bt into contact with the concave curved surface 71Cv of the cam surface 71C, the first switching pin 73 advances due to the biasing force of the coil spring 75.

The second switching pin 74 also has the same shape as the first switching pin 73, penetrates the same elongated hole 71a of the intake side switching drive shaft 71 in the same manner, and the biasing force of the coil spring 75 causes the base end cylindrical portion 74b to move. The conical end surface 74bt is pressed and engaged with the cam surface 71C to form a linear cam mechanism Ca, which is assembled (see FIG. 14).
When engaging the first switching pin 73 and the second switching pin 74 by engaging with the intake side switching drive shaft 71, the second switching pin 74 is assembled first.

  In addition, a movement restriction hole 71z, which is a long hole of a predetermined length in the axial direction, is formed on the right side of the intake rocker arm 72 on the right side of the intake side switching drive shaft 71 (see FIG. 11). The movement restriction pin 76 inserted into the small hole 3Ah formed in the cylindrical portion 3A of the head 3 penetrates the movement restriction hole 71z, so that the intake side switching drive shaft 71 moves axially between predetermined positions. Movement is restricted (see Fig. 4).

As shown in FIG. 14, the first switching pin 73 and the second switching pin 74 are arranged parallel to each other through the common long hole 71a of the intake side switching drive shaft 71.
FIG. 14 shows a state in which the center of the concave curved surface 71Cv of the cam surface 71C of the intake side switching drive shaft 71 is at the position of the first switching pin 73, and the first switching pin 73 has a conical end surface on the concave curved surface 71Cv. The second switching pin 74 is in a position advanced by abutting 73bt, and is in a position retracted by abutting the flat surface 71Cp of the cam surface 71C.

When the intake side switching drive shaft 71 moves to the right from this state, the conical end surface 73bt of the first switching pin 73 retreats from the center of the concave curved surface 71Cv up the inclined surface of the concave curved surface 71Cv and contacts the flat surface 71Cp. In the second switching pin 74, the conical end surface 74bt advances from the flat surface 71Cp down the inclined surface of the concave curved surface 71Cv and comes into contact with the center of the concave curved surface 71Cv.
In this way, the first switching pin 73 and the second switching pin 74 can be alternately advanced and retracted by the axial movement of the intake side switching drive shaft 71.
In order to urge the first and second switching pins 73 and 74 in the traveling direction, the coil spring 75 is interposed between the tip end cylindrical portions 73a and 74a and the intake side switching drive shaft 71. A coil spring may be interposed between the end faces of the end columnar portions 73b and 74b (end faces opposite to the conical end faces 73b and 74bt) and the bottom surface of the hole formed in the tubular portion 3A.

  4 to 6, at the center of the cylindrical portion 3B on the left side of the bearing wall 3V in the cylinder head 3, on the left side of the exhaust rocker arm 82, at the location corresponding to the lead groove cylindrical portion 53D of the exhaust side cam carrier 53. The cylindrical boss portion 3Bs is formed so as to project toward the lead groove cylindrical portion 53D, and the lead groove cylinder of the exhaust side cam carrier 53 is provided on the right side of the exhaust rocker arm 82 at the center of the cylindrical portion 3B on the right side of the bearing wall 3V. A cylindrical boss portion 3Bs is formed so as to project toward the lead groove cylindrical portion 53E at a location corresponding to the portion 53E.

Exhaust-side switch drive shaft 81, as shown in FIG. 11, at a site distant to the right the left end, the long hole 81a which penetrates the respective axis center _1, 81a ₂ is formed, the elongated holes 81a _1, 81a circular hole 81b _1, 81b ₂ extending through the axial center to the _second left are formed.
The widths of the long holes 81a ₁ and 81a ₂ and the inner diameters of the circular holes 81b ₁ and 81b ₂ are the same as those of the long holes 71a and the circular holes 71b of the intake side switching drive shaft 71.

One opening end face of the left long hole 81a ₁ of the exhaust side switching drive shaft 81 has a flat surface 81Cp that is edged and extends linearly with inclination, and a concave curved surface 81Cv that is formed by recessing in a predetermined shape on the left side thereof. And a cam surface 81C ₁ composed of

In addition, one opening end surface of the right long hole 81a ₂ of the exhaust side switching drive shaft 81 has a flat surface 81Cp that is edged and extends linearly with inclination, and a concave portion formed to a right side of the flat surface 81Cp by a predetermined shape. The cam surface 81C _{2 including the} curved surface 81Cv is configured.
The left and right long holes 81a ₁ and 81a _{2 of the} exhaust side switching drive shaft 81 and the left and right cam surfaces 81C ₁ and 81C ₂ are formed symmetrically.

Referring to FIG. 15, the first switching pin 83 is slidably engaged with the long hole 81a ₁ on the left side of the exhaust side switching drive shaft 81 through the intermediate connecting rod portion 83c, and the cam surface 81C. _The linear motion cam mechanism Cb is composed of 1.
Similarly, the second switching pin 84 slidably engages with the right long hole 81a ₂ of the exhaust side switching drive shaft 81, and the cam surface 81C ₂ constitutes the linear cam mechanism Cc (Fig. 6, see FIG. 11).

The assembling procedure is performed in the same manner as the assembling of the intake side switching drive shaft 71 and the first switching pin 73 using the circular holes 81b ₁ and 81b ₂ .
The first switching pin 83 and the second switching pin 84 are assembled at the same time.

The movement limiting hole 81z is long hole of a predetermined length right in the axial direction next to the right of the long hole 81a ₂ of the exhaust-side switching drive shaft 81 is formed, drilled in the cylindrical portion 3B of the cylinder head 3 The movement regulating pin 86 inserted into the formed small hole 3Bh penetrates the movement regulating hole 81z, whereby the movement of the exhaust side switching drive shaft 81 in the axial direction is regulated to the movement between predetermined positions (see FIG. 6). ).

Figure 15 is a right side of the flat surface 81Cp of the left cam surface 81C ₁ of the exhaust-side switching drive shaft 81 shows a state in which the position of the first switching pin 83, the first switching pin 83 is a flat surface 81Cp 6 is in a position where the conical end surface 83bt comes into contact with and retracts, and at this time, the second switching pin 84 is in a position where the conical end surface 83bt comes into contact with the concave curved surface 81Cv of the right cam surface 81C ₂ (FIG. 6). reference).

When the exhaust side switching drive shaft 81 moves to the right from this state, the conical end surface 83bt of the first switching pin 83 advances from the flat surface 81Cp down the inclined surface of the concave curved surface 81Cv to the center of the concave curved surface 81Cv, The conical end surface 84bt of the second switching pin 84 goes up from the center of the concave curved surface 81Cv to the sloped surface of the concave curved surface 81Cv and contacts the flat surface 81Cp and retreats.
In this way, the first switching pin 83 and the second switching pin 84 can be alternately advanced and retracted by the axial movement of the exhaust side switching drive shaft 81.

As shown in FIG. 8, the intake side cam switching mechanism 70 and the exhaust side cam switching mechanism 80 are located closer to the crankshaft 10 than the central axis line Ci of the intake side cam shaft 42 and the central axis line Ce of the exhaust side cam shaft 52. The intake-side cam switching mechanism 70, which is disposed, includes the intake-side plane Si that includes the center axis Ci of the intake-side camshaft 42 and is parallel to the cylinder axis Lc and the center-axis Ce of the exhaust-side camshaft 52 that is parallel to the cylinder axis Lc. It is arranged between the exhaust-side plane Se parallel to the axis Lc.

  On the right side wall 3R of the cylinder head 3, an intake side hydraulic actuator 77 for axially moving the intake side switching drive shaft 71 is provided to project, and an exhaust side hydraulic actuator for axially moving the exhaust side switching drive shaft 81. 87 is provided so as to project side by side behind the intake hydraulic actuator 77 (see FIGS. 1 and 4).

The movement of the intake side cam switching mechanism 70 when the intake side cam carrier 43 is moved to switch the first cam lobe 43A and the second cam lobe 43B to act on the intake rocker arm 72 is shown in FIG. A description will be given based on an explanatory diagram.
FIG. 16 sequentially shows the operation process of the main members of the intake side cam switching mechanism 70 with time.

  In the state shown in (1) of FIG. 16, the intake side cam carrier 43 is at the left side position, the second cam lobe 43B acts on the intake rocker arm 72, and the valve operating characteristic set in the cam profile of the second cam lobe 43B. The intake valve 41 is operating in accordance with.

At this time, the intake side switching drive shaft 71 is also at the left side position, the concave curved surface 71Cv of the cam surface 71C is at the position of the first switching pin 73, and the first switching pin 73 contacts the concave curved surface 71Cv to proceed. It is engaged with the annular lead groove 44c of the lead groove cylindrical portion 43D of the intake side cam carrier 43.
The second switching pin 74 abuts on the flat surface 71Cp of the cam surface 71C, moves backward, and is separated from the lead groove 44.
Therefore, the intake side cam carrier 43, which is spline-fitted to the intake side cam shaft 42 and rotates, has the first switching pin 73 engaged with the annular lead groove 44c formed over the entire circumference in the circumferential direction. It does not move in the axial direction and is kept in place.

  When the intake side switching drive shaft 71 is moved to the right by the intake side hydraulic actuator 77 from this state, the first switching pin 73 is guided by the inclined surface of the concave curved surface 71Cv and retreats, and the second switching pin 74 is moved to the flat surface 71Cp. Is guided by the inclined surface of the concave curved surface 71Cv (see (2) in FIG. 16) and the first switching pin 73 and the second switching pin 74 are separated from the lead groove 44 by substantially the same distance ((3) in FIG. 16). Next, instead of the first switching pin 73 coming into contact with the flat surface 71Cp and further retreating, the second switching pin 74 comes into contact with the concave curved surface 71Cv and proceeds further to advance to the right shift lead of the lead groove cylindrical portion 53D. It engages with the groove 44r (see (4) in FIG. 16).

When the second switching pin 74 engages with the right shift lead groove 44r, the intake-side cam carrier 43 is guided by the right shift lead groove 44r and moves axially rightward while rotating (see (4) and (4 in FIG. 16). 5)).
When the intake-side cam carrier 43 moves to the right, the second switching pin 74 engages with the annular lead groove 44c, so that the intake-side cam carrier 43 is maintained at the predetermined position moved to the right (FIG. 16). (5)), at this time, the first cam lobe 43A acts on the intake rocker arm 72 instead of the second cam lobe 43B, and the intake valve 41 operates according to the valve operating characteristic set in the cam profile of the first cam lobe 43A. To do.

Thus, by moving the intake side switching drive shaft 71 to the right, the cam lobe acting on the intake valve 41 can be switched from the second cam lobe 43B to the first cam lobe 43A.
Further, from this state, by conversely moving the intake side switching drive shaft 71 to the left, the second switching pin 74 retracts and separates from the annular lead groove 44c, and the first switching pin 73 advances and shifts to the left. The intake side cam carrier 43 is moved leftward by being engaged with the lead groove 44l and guided by the left shift lead groove 44l, and the cam lobe acting on the intake valve 41 is switched from the first cam lobe 43A to the second cam lobe 43B. be able to.

Next, the movement of the exhaust side cam switching mechanism 80 will be described based on the explanatory view of FIG.
In the state shown in (1) of FIG. 17, the exhaust side cam carrier 53 is at the left side position, the second cam lobe 53B acts on the intake rocker arm 72, and the valve operating characteristic set in the cam profile of the second cam lobe 53B. The intake valve 41 is operating in accordance with.

At this time, the exhaust side switching drive shaft 81 is also at the left side position, the first switching pin 83 comes into contact with the flat surface 81Cp of the left side cam surface 81C1 and retreats away from the left side lead groove 54, and the right side cam surface. concave surface 81Cv of the surfaces 81C ₂ is in the position of the second switching pin 84, the right lead groove 55 of the second switching pin 84 is advanced in contact with the concave surface 81Cv exhaust cam carrier 53 an annular lead groove 55c , The exhaust side cam carrier 53 is maintained at a predetermined position without moving in the axial direction.

  When the exhaust side hydraulic actuator 87 moves the exhaust side switching drive shaft 81 to the right from this state, the second switching pin 84 retreats while being guided by the inclined surface of the concave curved surface 81Cv, and the first switching pin 83 moves to the flat surface 81Cp. 17 is guided by the inclined surface of the concave curved surface 81Cv (see (2) in FIG. 17), and the first switching pin 83 and the second switching pin 84 are separated from the lead grooves 54 and 55 by substantially the same distance (see (2 in FIG. 17). 3)), then, instead of the second switching pin 84 contacting the flat surface 81Cp and further retreating, the first switching pin 83 contacts the concave curved surface 81Cv and advances further to shift the left lead groove 54 to the right. It engages with the lead groove 54r (see (4) in FIG. 17).

When the first switching pin 83 engages with the right shift lead groove 54r, the exhaust side cam carrier 53 is guided by the right shift lead groove 54r and rotates and moves axially to the right ((4), (4) in FIG. 17). 5)).
When the exhaust side cam carrier 53 moves to the right, the first switching pin 83 engages with the annular lead groove 54c, so that the exhaust side cam carrier 53 is maintained at the predetermined position moved to the right (FIG. 17). (5)), at this time, the first cam lobe 53A acts on the exhaust rocker arm 82 instead of the second cam lobe 53B, and the exhaust valve 51 operates according to the valve operating characteristic set in the cam profile of the first cam lobe 53A. To do.

Thus, by moving the exhaust side switching drive shaft 81 to the right, the cam lobe acting on the exhaust valve 51 can be switched from the second cam lobe 53B to the first cam lobe 53A.
Further, from this state, by moving the exhaust side switching drive shaft 81 to the left, the first switching pin 83, the second switching pin 84 retracts and separates from the annular lead groove 54c, and the second switching pin 84 moves. The exhaust side cam carrier 53 moves leftward by being guided by the left shift lead groove 55l as it advances, engaging the left shift lead groove 55l, and moving the cam lobe acting on the exhaust valve 51 from the first cam lobe 43A to the first cam lobe 43A. You can switch to 2 Cam Rob 43B.

As described above, the embodiment of the variable valve operating device according to the present invention described in detail has the following effects.
As shown in FIG. 10 (and FIG. 5), the idle chain sprocket 62 is provided at a position that axially overlaps the bearing portion 3UA of the bearing wall 3U and the camshaft holder 33, so that the idle gear 61 is axially supported by the bearing. The intake side driven gear 47 and the exhaust side driven gear 57 which mesh with the idle gear 61 can also be brought close to the bearing portion 3UA, and the intake side camshaft 42 having a shorter protruding length from the bearing portion 3UA can be provided. The exhaust-side camshaft 52 can be fitted and arranged at each end of the camshaft 52, and the axial width of the internal combustion engine E can be suppressed to a small size, and the internal combustion engine can be downsized.

  As shown in FIGS. 4 and 7, the camshaft holder 33 includes four fastening parts 33a, 33b on both sides of the intake side camshaft 42 and two fastening parts 33c, 33d on the both sides of the exhaust side camshaft 52. The four fastening bolts 38a, 38b, 38c and 38d are fastened to the bearing portion 3UA of the bearing wall 3U by fastening bolts 38a, 38b, 38c and 38d, respectively. , 38d fasten the fastening parts 33a, 33d on both sides with the idle chain sprocket 62 interposed therebetween, so that the two outer fastening bolts 38a, 38d at the same axial position as the idle chain sprocket 62 are By avoiding the sprocket 62 and locating on both sides of the sprocket without projecting upward, it is possible to prevent the upper part of the cylinder head 3 of the internal combustion engine from projecting upward, and to prevent the internal combustion engine from increasing in size. That.

  As shown in FIG. 4, the bearing wall 3U and the camshaft holder 33 have bulging portions 3UB and 33B bulging inward in the axial direction between the intake side camshaft 42 and the exhaust side camshaft 52, Of the four fastening bolts 38a, 38b, 38c, 38d, the inner two fastening bolts 38b, 38c fasten the fastening portions 33b, 33c provided on the bulging portions 3UB, 33B, so that the inner two fastenings The bolts 38b, 38c use the space between the intake-side camshaft 42 and the exhaust-side camshaft 52 to bulge the bearing wall 3U and the idle chain sprocket 62 in the bulged portions 3UB, 33B of the camshaft holder 33. It is possible to fasten the fastening portions 3UB and 33B that are avoided in the axial direction, and the camshaft holder 33 can be compactly mounted without increasing the size of the internal combustion engine E.

  As shown in FIG. 4, the outer diameter of the lead groove cylindrical portion 43D in which the lead groove 44 of the intake side cam carrier 43 is formed is larger than the outer diameter of the base circle of the same diameter of the first cam lobe 43A and the second cam lobe 43B. The outer diameters of the lead groove cylindrical portions 53D, 53E, which are small and in which the lead grooves 54, 55 of the exhaust side cam carrier 53 are formed, are smaller than the outer diameter of the basic circle of the same diameter of the first cam lobe 53A and the second cam lobe 53B. The bulging portions 3UB and 33B that are small and bulge inward in the axial direction between the bearing wall 3U and the intake-side camshaft 42 of the camshaft holder 33 and the exhaust-side camshaft 52 are provided on the intake-side cam carrier 43 and the exhaust-side cam. Since the axial position of at least one of the lead groove cylindrical portions 43D of the carrier 53 is the same, the intake side cam carrier 43 and the exhaust side cam carrier 53 sandwiching the bulging portions 3UB and 33B are cam lobes 43A, 43B, 53A and 53B. As close to each other as possible without interfering with , It is possible to reduce the size of the internal combustion engine.

  Although the variable valve operating device according to the embodiment of the present invention has been described above, the aspect of the present invention is not limited to the above-described embodiment, and is implemented in various aspects within the scope of the present invention. It includes things.

For example, in the present embodiment, in the cam switching mechanism, the switching drive shaft is moved in the axial direction to move the switching pin forward and backward by the direct acting cam mechanism. The switching pin may be moved back and forth in a direction perpendicular to the axial direction by rotating the surface.
Although the hydraulic actuator is used to drive the switching drive shaft, an electromagnetic solenoid, an electric motor, or the like may be used.

E ... Internal combustion engine, M ... Transmission,
1 ... Crank case, 2 ... Cylinder block, 3 ... Cylinder head, 3g ... Gear chamber,
10 ... Crank shaft, 11 ... Main shaft, 12 ... Counter shaft, 33 ... Cam shaft holder, 33a, 33b, 33c, 33d ... Fastening part, 34 ... Cam shaft holder, 38a, 38b, 38c, 38d ... Fastening bolt, 39a , 39b, 39c, 39d ... Fastening bolts,
40 ... Variable valve device,
41 ... intake valve, 42 ... intake side camshaft, 42A ... left side flange part, 42B ... bearing part, 42C ... right side flange part, 42D ... spline shaft part,
43 ... Intake side cam carrier, 43A ... First cam lobe, 43B ... Second cam lobe, 43C ... Bearing cylindrical portion, 43D ... Lead groove cylindrical portion, 44 ... Lead groove, 47 ... Intake side driven gear,
51 ... Exhaust valve, 52 ... Exhaust side cam shaft, 52A ... Left side flange part, 52B ... Bearing part, 52C ... Right side flange part, 52D ... Spline shaft part,
53 ... Exhaust side cam carrier, 53A ... First cam lobe, 53B ... Second cam lobe, 53C ... Bearing cylindrical portion, 53D ... Lead groove cylindrical portion, 53E ... Lead groove cylindrical portion, 54 ... Left lead groove, 55 ... Right lead Groove, 56 ... cap member, 57 ... exhaust side driven gear,
61 ... Idle gear, 62 ... Idle chain sprocket, 63 ... Bearing, 64 ... Bolt, 65 ... Cylindrical support shaft, 66 ... Cam chain, 67 ... Drive chain sprocket,
70 ... intake side cam switching mechanism, 71 ... intake side switching drive shaft, 72 ... intake rocker arm, 73 ... first switching pin, 74 ... second switching pin,
80 ... Exhaust side cam switching mechanism, 81 ... Exhaust side switching drive shaft, 82 ... Exhaust rocker arm, 83 ... First switching pin, 84 ... Second switching pin.

Claims (3)

The intake side camshaft (42) and the exhaust side camshaft (52) are equipped with a DOHC structure valve mechanism that is rotatably supported.
The intake side driven gear (47) and the exhaust side driven gear are respectively attached to the ends of the intake side camshaft (42) and the exhaust side camshaft (52) that penetrate the bearing wall (3U) and the camshaft holder (33). (57) is fitted,
An idle gear (61) that meshes with both the intake side driven gear (47) and the exhaust side driven gear (57) is rotatably supported by a support shaft (65) provided in the cylinder head (3).
An idle chain sprocket (62) is provided adjacent to the bearing wall (3U) side axially inside coaxially with the idle gear (61),
A cam chain (66) is bridged between the idle chain sprocket (62) and the drive chain sprocket (67) fitted to the crankshaft (10),
In an internal combustion engine in which the power of the crankshaft (10) is transmitted to the intake side camshaft (42) and the exhaust side camshaft (52),
The idle chain sprocket (62) is provided at a position that axially overlaps the bearing portion (3UA) of the bearing wall (3U) and the camshaft holder (33) ,
The intake side camshaft (42) and the exhaust side camshaft (52) are axially supported by the bearing portion (3UA) of the bearing wall (3U) at the same axial position as the idle chain sprocket (62). The camshaft holder (33) is fastened and attached to the bearing portion (3UA) of the bearing wall (3U) by fastening bolts (38a, 38b, 38c, 38d),
Of the fastening bolts (38a, 38b, 38c, 38d), the fastening bolts (38a, 38d) arranged at the end of the camshaft holder (33) are located on both sides of the idle chain sprocket (62). Fasten the fastening parts (33a, 33d) of
The bearing wall (3U) and the camshaft holder (33) have a bulging portion (3UB, 3UB, which bulges axially inward between the intake side camshaft (42) and the exhaust side camshaft (52). 33B),
A cylindrical member that is fitted to the outer circumference of the intake-side camshaft (42) such that relative rotation is prohibited and is slidable in the axial direction, and a plurality of cam lobes (43A, 43B) having different cam profiles are provided on the outer circumferential surface. An intake side cam carrier (43) having a lead groove cylindrical portion (43D) formed adjacent to each other in the axial direction and having a lead groove (44) with which a switching pin (73, 74) engages,
A cylindrical member that is fitted to the outer circumference of the exhaust side camshaft (52) such that relative rotation is prohibited and is slidable in the axial direction, and a plurality of cam lobes (53A, 53B) having different cam profiles are provided on the outer circumferential surface. An exhaust side cam carrier (53) having lead groove cylindrical portions (53D, 53E) formed adjacent to each other in the axial direction and having lead grooves (54, 55) with which the switching pins (83, 84) engage is formed. ) And
The bulging portion (3UB, 33B), the intake side cam carrier (43) and the exhaust side cam carrier (53) at least one of the lead groove cylindrical portion (43D), the axial position is the same. Internal combustion engine. At least one fastening bolt (38b, 38c) on the inner side of the fastening bolts (38a, 38b, 38c, 38d) has a fastening portion (33b, 33c) provided on the bulging portion (3UB, 33B). The internal combustion engine according to claim 1 , wherein the internal combustion engine is engaged. A cam switching mechanism (70, 70) for switching the cam by moving the intake side cam carrier (43) and the exhaust side cam carrier (53) respectively by advancing and retracting the switching pin into and out of the lead groove. 80) and
The outer diameter of the lead groove cylindrical portion (43D, 53D, 53E) in which the lead grooves (44, 54, 55) are formed is a basic circle of the same diameter of a plurality of cam lobes (43A, 43B, 53A, 53B). The internal combustion engine according to claim 2 , wherein the internal diameter is smaller than the outer diameter.

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